Mining environments, particularly open pit surface mining environments, present unique challenges to maintaining safe and efficient operation of vehicles. The workhorse of a modern surface mine is a mine haul truck, which is a dump truck capable of hauling hundreds of tons of material. Haul trucks are some of the largest land vehicles ever built. As such, they are characterized by limited maneuverability, relatively slow acceleration and deceleration, poor sight lines on every side of the vehicle, and relatively low fuel efficiency. Other vehicles, such as shovels, dozers, bucket wheel excavators, and other equipment are each similarly difficult to control. The vehicles are large, with wide turning radii, and slow braking and accelerating capabilities.
At any one time, a large number of vehicles may be working within a particular mine. During operation, each vehicle will move to different locations within the mine to retrieve material, dump material, or to assist in a number of different operations. While navigating between the different locations, each vehicle will travel along a particular route following one or more of the mine's roadways or designated throughways. In some cases, a centralized control system is arranged to assign each vehicle to a particular route through the mine.
Because a large number of vehicles may be operating in the mine simultaneously, the likelihood of a first vehicle interfering with the movement of a second vehicle (or occupying a resource desired by the second vehicle) is relatively high. This is referred to as contention, and is usually managed by the provision of traffic control systems located at the mine's intersections, single lane roadways, dump sites, bridges, or other locations where traffic must be managed. Example traffic control systems include stop signs, traffic lights, rights of way, one-way restrictions, and speed limits.
Contention between mobile equipment in open pit and underground mines can be a significant source of losses in machine productivity, increases in fuel consumption, and increased maintenance costs. When a vehicle encounters a location with potential contention the vehicle may need to slow down. In most cases, though, the vehicle is forced to stop and wait for an opportunity when it is safe and procedure dictates that the vehicle can proceed. The delays can be extended when there are multiple vehicles or pieces of equipment at the point of potential contention.
Large mining vehicles are very slow to accelerate. As a result, the cost of bringing equipment to a complete stop, even for a few seconds, is very high. For example, from a dead stop an empty truck on a flat grade may take 45 seconds or more to reach nominal speed. The situation is worse for equipment going uphill, loaded, or uphill loaded.
One situation where contention is most detrimental involves a loaded haul truck that is stopped on a positive grade. In that scenario the loaded truck will have to depend on the truck's brakes to hold the truck still on the ramp. When it is safe to move, the truck will be forced to use the truck's engine at full power in order to get the truck moving again. This consumes fuel at a rapid rate and puts stress on mechanical and electrical components of the truck.
The cost of contention can, therefore, be significant. Because mining haulage vehicles have exceptionally high Gross Vehicle Mass (e.g., greater than 500 tons), the costs associated with accelerating and stopping a truck can be very high. It is therefore beneficial to avoid unnecessarily aggressive traveling that does not result in increased production.